Vasudevi Reddy and Colwyn Trevarthen (2004)
Zero to Three, January 2004, Volume 24, No. 3, 9-15.
Sadly, Zero to Three have asked that I remove this article from the blog and request that you view it on their own web site. I was not aware I was in breach of their rights as it is fully sourced and I make no claim to the contrary.
I have formally requested permission to have the article back on our blog, and will re-post if they agree. I did not come by the article via their web site so I am unable to provide a URL, but when I search it is available to download elsewhere. Please do not publish without seeking their permission.
I'm disappointed with the response from Zero to Three, but strongly recommend visiting their excellent website.